Current understanding of the physiological role of messenger ribonucleoprotein (mRNP) is hampered by the lack of suitable assays for the function of specific proteins bound to messenger RNA (mRNA) in these particles. In the proposed study, the slime mold, Physarum polycephalum, is employed as a unique biological system for the investigation of the structure and function of two divergent types of mRNP, translationally-active mRNP from the polysomes of vegetative plasmodia and stored mRNP from the post-ribosomal supernatant of a dormant stage. The specific objectives are to develop methods for the isolation of polysomal and stored mRNP using cell fractionation techniques and oligo(dT)-cellulose chromatography, characterization and comparison of the RNA and protein moieties of polysomal and stored mRNP, analysis of the formation of stored mRNP during dormancy and its activation during germination by radioactive labelling methods, comparison of the translational efficiency and relative metabolic stability of polysomal and stored mRNP, and the development of assay systems to test the function of mRNP proteins in translation and stability. It is envisioned that this study will ellucidate structural differences exhibited by mRNA in different cellular states and provide roles for at least some of the proteins associated with this molecule.